Here’s an unlikely parallel – between the Liberal Democrats and the French Communist Party. In the run-up to the 1981 Presidential election campaign, polls gave the PCF cause for encouragement. But as with the Lib Dems in 2010, it proved to be a false dawn.

Also as with the Lib Dems, the PCF took a junior role in the government – filling a number of cabinet posts.

French conservatives were aghast, condemning Francois Mitterrand for doing a deal with the devil. They needn’t have worried – the experience of government was not a happy one for the PCF. Within a few years they were out of power and well on the way to irrelevance.

Coalition is rarely a comfortable experience for minor parties, but what is less appreciated is that it can be a downright fatal one. The Communists in France, the Free Democrats in Germany and the Progressive Democrats in Ireland are all examples of the worst that can happen.